JP6689100B2 - Mixture, functional layer, photoelectric conversion element and perovskite stabilizer - Google Patents

Description

  The present invention relates to a mixture containing a perovskite type compound, a functional layer, a photoelectric conversion element, and a perovskite stabilizer used for stabilizing a perovskite type compound.

A solar cell has been attracting a great deal of attention as it can convert sunlight, which is a renewable energy, into highly usable electric energy. Silicon is the mainstream material for the photoelectric conversion layer of solar cells, but since silicon is expensive, the manufacturing cost is high, which is a factor that prevents the spread of solar cells. On the other hand, organic-inorganic perovskite type compounds have recently been expected as a photoelectric conversion material for solar cells. The organic-inorganic perovskite type compound is composed of an organic cation such as methylammonium, a divalent metal ion such as Pb ²⁺ and a halogen ion, and these ions form the same crystal structure (perovskite type structure) as perovskite (perovskite). It is a compound that is regularly arranged so that lead methylammonium iodide (CH ₃ NH ₃ PbI ₃ ) is known. Since organic-inorganic perovskite type compounds can be formed into a film by the solution coating method using abundant raw materials, it is expected to contribute greatly to the cost reduction of solar cells, and it will be put to practical use as a photoelectric conversion material. Research is being actively pursued.

これに対して、非特許文献３には、光電変換層を構成するヨウ化鉛メチルアンモニウムの結晶間に、アルキルホスホン酸アンモニウムクロライドによる架橋構造を形成することにより、電池特性の経時劣化が抑制されたことが報告されている。 Here, what is a development subject in the solar cell using the organic-inorganic perovskite type compound is improvement of stability of characteristics. That is, it is known that the organic-inorganic perovskite solar cell undergoes photodegradation in which the photoelectric conversion efficiency gradually decreases during continuous irradiation of light, and the degradation is accelerated especially in a high humidity environment. . The cause is considered to be involved in the reaction represented by the following formula, and lead methylammonium iodide is converted into a perovskite hydrate, which is disadvantageous for photoelectric conversion, or decomposed into a low-molecular component, so that the element It is presumed that photo-deterioration of characteristics occurs (see, for example, Non-Patent Documents 1 and 2).

On the other hand, in Non-Patent Document 3, by forming a crosslinked structure by ammonium alkylphosphonate chloride between the crystals of lead methylammonium iodide constituting the photoelectric conversion layer, deterioration of battery characteristics over time is suppressed. It has been reported.

P. V. Kamat et al. JACS, 137, 1530 (2015). Bertrand Philippe et al. Chem. Mater., 27, 1720 (2015). Xiong Li et al. NCEM, [online] 17 AUGUST 2015, <URL: http://www.nature.com/naturechemistry>

On the other hand, the present inventors have been earnestly studying in order to elucidate the mechanism of characteristic deterioration of the organic-inorganic perovskite type solar cell, and by continuous light irradiation, the decomposition reaction is represented by the following formula. It was found that the reaction (PbI ₂ → Pb + I ₂ ) proceeded, and the accumulated metallic lead Pb was a factor of characteristic deterioration over time. That is, when metallic lead is accumulated in the photoelectric conversion layer by the following reaction, even if carriers are generated by photoexcitation of the photoelectric conversion layer, the carriers are trapped in metallic lead with a high probability and disappeared by recombination. As a result, it was clarified that the efficiency of carrier recovery from the electrode was low.

In Non-Patent Documents 1 and 2 above, lead methylammonium iodide is converted to perovskite hydrate (CH ₃ NH ₃ ) ₄ PbI ₆ · 2H ₂ O) or a low molecular weight component (CH ₃ NH ₂ , HI) is used. , PbI ₂ ) and the device characteristics are degraded. However, it is not described in each document that the above reaction further progresses and metallic lead Pb is accumulated, which causes deterioration of device characteristics. Further, Non-Patent Document 3 describes that deterioration of characteristics over time is suppressed by forming a crosslinked structure between crystals of lead methylammonium iodide with a specific ammonium salt. However, Non-Patent Document 3 also does not describe a mechanism of characteristic deterioration focusing on metallic lead Pb. In addition, the formation of the above-mentioned cross-linking structure does not suppress the characteristic deterioration due to metallic lead Pb, and it is impossible to sufficiently realize the long life of the element and the stable driving in a high humidity environment.

  Therefore, in order to solve the problems of the prior art, the present inventors have studied for the purpose of providing a mixture and a functional layer in which the generation of a metal from a perovskite compound is suppressed, and a perovskite stabilizer. I advanced. Further, the present inventors have conducted studies for the purpose of providing a photoelectric conversion element which is capable of suppressing deterioration of element characteristics over time, has a long life, and can be stably driven even in a high humidity environment.

  As a result of intensive studies to solve the above problems, the present inventors have found that when a quinone compound is mixed with a perovskite type compound, the reduction of metal ions released from the perovskite type structure to a metal is effectively suppressed. It was found that the formation of metal is suppressed. Further, it was found that by using this mixture as a material for the photoelectric conversion layer, a photoelectric conversion element having a long life and capable of stable driving even in a high humidity environment can be obtained. Furthermore, they have found that the quinone-based compound does not affect the crystal structure and light absorption characteristics of the perovskite-type compound and is suitable as a stabilizer for the perovskite-type compound. Specifically, the present invention has the following configurations.

（一般式（１−１）〜（１−３）において、Ｒ¹〜Ｒ⁴は各々独立に水素原子または置換基を表す。Ｒ¹とＲ²、Ｒ³とＲ⁴はそれぞれ互いに結合して環状構造を形成していてもよい。）
［４］ 前記一般式（１−１）〜（１−３）のＲ¹〜Ｒ⁴が水素原子である［３］に記載の混合物。
［５］ 前記ペロブスカイト型化合物は、有機無機ペロブスカイト型化合物である［１］〜［４］のいずれか１項に記載の混合物
［６］ 前記有機無機ペロブスカイト型化合物は、ヨウ化鉛系ペロブスカイト型化合物である［５］に記載の混合物。
［７］ 前記有機無機ペロブスカイト型化合物は、下記一般式（２）または下記一般式（３）で表される化合物である［５］に記載の混合物。
一般式（２）
ＡＢＸ₃
［一般式（２）において、Ａは有機カチオンを表し、Ｂは２価の金属イオンを表し、Ｘはハロゲンイオンを表す。３つのＸは互いに同じであっても異なっていてもよい］
一般式（３）
Ａ² ₂Ａ¹ _n-1Ｂ_nＸ_3n+1
［一般式（３）において、Ａ¹は有機カチオンを表し、Ａ²は、Ａ¹が表す有機カチオンよりも炭素数が大きい有機カチオンを表す。Ｂは２価の金属イオンを表し、Ｘはハロゲンイオンを表す。ｎは１〜１０の整数である。複数のＡ²同士および複数のＸ同士は、それぞれ互いに同じであっても異なっていてもよい。Ａ¹およびＢがそれぞれ複数存在するとき、Ａ¹同士およびＸ同士は、それぞれ互いに同じであっても異なっていてもよい。］
［８］ 前記一般式（２）のＡおよび前記一般式（３）のＡ¹は、下記一般式（４）で表されるアンモニウムである［７］に記載の混合物。
一般式（４）
（Ｒ¹⁰ ₄Ｎ）⁺
［一般式（４）において、Ｒ¹⁰は水素原子または置換もしくは無置換のアルキル基を表し、４つのＲ¹⁰の少なくとも１つは置換もしくは無置換のアルキル基である。］
［９］ 前記一般式（４）のＲ¹⁰はメチル基である［８］に記載の混合物。
［１０］ 前記一般式（３）のＡ²は、下記一般式（５）で表されるアンモニウムである［７］〜［９］のいずれか１項に記載の混合物。
一般式（５）
（Ｒ¹¹ ₄Ｎ）⁺
［一般式（５）において、Ｒ¹¹は水素原子または置換基を表し、４つのＲ¹¹の少なくとも１つは、炭素数が２以上の置換基である。］
［１１］ 前記一般式（２）および前記一般式（３）のＢはＰｂ²⁺である［７］〜［１０］のいずれか１項に記載の混合物。
［１２］ 前記一般式（２）または前記一般式（３）のＸはＩ^-である［７］〜［１１］のいずれか１項に記載の混合物。
［１３］ 前記有機無機ペロブスカイト型化合物は、前記一般式（２）で表される化合物である［７］〜［１２］のいずれか１項に記載の混合物
［１４］ 前記混合物における前記キノン系化合物の含有量が、前記ペロブスカイト型化合物とのモル比（［キノン系化合物］／［ペロブスカイト型化合物］）で１／２００以上である［１］〜［１３］のいずれか１項に記載の混合物。 [1] A mixture containing a quinone compound and a perovskite compound.
[2] The mixture according to [1], wherein the quinone compound is a compound having a 6-membered quinone skeleton.
[3] The mixture according to [1] or [2], wherein the quinone compound is a compound represented by any of the following general formulas (1-1) to (1-3).

(In formulas (1-1) to (1-3), R ^{1 to} R ⁴ each independently represent a hydrogen atom or a substituent. R ¹ and R ² , and R ³ and R ⁴ are bonded to each other. It may form a ring structure.)
[4] The mixture according to [3], wherein R ^{1 to} R ^{4 in the} general formulas (1-1) to (1-3) are hydrogen atoms.
[5] The mixture according to any one of [1] to [4], wherein the perovskite-type compound is an organic-inorganic perovskite-type compound [6] The organic-inorganic perovskite-type compound is a lead iodide-based perovskite-type compound The mixture according to [5].
[7] The mixture according to [5], wherein the organic-inorganic perovskite compound is a compound represented by the following general formula (2) or the following general formula (3).
General formula (2)
ABX ₃
[In the general formula (2), A represents an organic cation, B represents a divalent metal ion, and X represents a halogen ion. The three Xs may be the same or different from each other]
General formula (3)
A ² ₂ A ¹ _n-1 B _n X _{3n + 1}
[In the general formula (3), A ¹ represents an organic cation, and A ² represents an organic cation having a carbon number larger than that of the organic cation represented by A ¹ . B represents a divalent metal ion, and X represents a halogen ion. n is an integer of 1-10. The plurality of A ^2's and the plurality of X's may be the same or different from each other. When a plurality of A ¹ and B are present, A ^1's and X's may be the same or different from each other. ]
[8] The mixture according to [7], wherein A in the general formula (2) and A ¹ in the general formula (3) are ammonium represented by the following general formula (4).
General formula (4)
(R ¹⁰ ₄ N) ⁺
[In the general formula (4), R ¹⁰ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and at least one of the four R ¹⁰ is a substituted or unsubstituted alkyl group. ]
[9] The mixture according to [8], wherein R ^{10 in the} general formula (4) is a methyl group.
[10] The mixture according to any one of [7] to [9], wherein A ² in the general formula (3) is ammonium represented by the following general formula (5).
General formula (5)
(R ¹¹ ₄ N) ⁺
[In General Formula (5), R ¹¹ represents a hydrogen atom or a substituent, and at least one of the four R ¹¹ is a substituent having 2 or more carbon atoms. ]
[11] The mixture according to any one of [7] to [10], wherein B in the general formula (2) and the general formula (3) is Pb ²⁺ .
[12] The mixture according to any one of [7] to [11], wherein X in the general formula (2) or the general formula (3) is I ⁻ .
[13] The organic-inorganic perovskite-type compound is the compound represented by any one of [7] to [12], which is a compound represented by the general formula (2). [14] The quinone-based compound in the mixture. The mixture according to any one of [1] to [13], wherein the content thereof is 1/200 or more in a molar ratio with the perovskite type compound ([quinone compound] / [perovskite compound]).

[15] A functional layer comprising the mixture according to any one of [1] to [14].
[16] The functional layer according to [17], which is a photoelectric conversion layer.

[17] A photoelectric conversion device having a layer containing a quinone compound and a perovskite compound.
[18] The photoelectric conversion element according to claim 15, wherein the layer containing the quinone-based compound and the perovskite-type compound comprises the mixture according to any one of [1] to [14].
[19] The photoelectric conversion element according to [17] or [18], wherein the layer containing the quinone compound and the perovskite compound is a photoelectric conversion layer.
[20] The perovskite-type compound contains Pb ²⁺ , and the quinone-based compound and the perovskite-type compound after irradiation with white light of 100 mW / cm ² for 1000 hours under the condition of a temperature of 298 K and a relative humidity of 50% The photoelectric conversion element according to any one of [17] to [19], wherein the content of metallic lead in the layer containing is 10% or less.

（一般式（１−１）〜（１−３）において、Ｒ¹〜Ｒ⁴は各々独立に水素原子または置換基を表す。Ｒ¹とＲ²、Ｒ³とＲ⁴はそれぞれ互いに結合して環状構造を形成していてもよい。） [21] A perovskite stabilizer containing a quinone compound.
[22] The perovskite stabilizer according to [21], wherein the quinone compound is a compound represented by any one of the following general formulas (1-1) to (1-3).

(In formulas (1-1) to (1-3), R ^{1 to} R ⁴ each independently represent a hydrogen atom or a substituent. R ¹ and R ² , and R ³ and R ⁴ are bonded to each other. It may form a ring structure.)

  The mixture of the present invention contains a quinone-based compound together with a perovskite-type compound, whereby the reduction of metal ions liberated from the perovskite-type compound is effectively suppressed by the oxidation action of the quinone-based compound, and the generation of metal is suppressed. . Further, according to the photoelectric conversion element of the present invention, since the layer containing the perovskite type compound contains the quinone compound, the generation of metal in the layer and the deterioration of the characteristics over time due to the metal are significantly suppressed. As a result, it is possible to realize a photoelectric conversion element which has a long life and can be stably driven even in a high humidity environment.

It is a schematic sectional drawing which shows the example of a layer structure of a photoelectric conversion element. 3 is an X-ray diffraction spectrum of a photoelectric conversion layer containing lead methylammonium iodide and benzoquinone formed in Example 1 and a photoelectric conversion layer containing lead methylammonium iodide formed in Comparative Example 1. 3 is a light absorption spectrum of a photoelectric conversion layer containing lead methylammonium iodide and benzoquinone formed in Example 1 and a photoelectric conversion layer containing lead methylammonium iodide formed in Comparative Example 1. The graph which shows the initial element characteristic of the photoelectric conversion element which contains lead methylammonium iodide and benzoquinone of Example 1 in the photoelectric conversion layer, and the photoelectric conversion element which contains lead methylammonium iodide of Comparative Example 1 in the photoelectric conversion layer. Is. The photoelectric conversion efficiency of the photoelectric conversion element containing lead methylammonium iodide and benzoquinone of Example 1 in the photoelectric conversion layer and the photoelectric conversion efficiency of the photoelectric conversion element of Comparative Example 1 containing lead methylammonium iodide in the photoelectric conversion layer were changed with time. It is a graph shown. The graph which shows the initial element characteristic of the photoelectric conversion element which contains the lead methylammonium iodide and benzoquinone of Example 2 in the photoelectric conversion layer, and the photoelectric conversion element which contains the lead methylammonium iodide of the comparative example 2 in the photoelectric conversion layer. Is. The photoelectric conversion element containing lead methylammonium iodide and benzoquinone in Example 2 in the photoelectric conversion layer and the photoelectric conversion element containing lead methylammonium iodide in Comparative Example 2 in the photoelectric conversion layer were continuously irradiated with white light. It is a graph which shows the time-dependent change of the photoelectric conversion efficiency at this time. Regarding the photoelectric conversion element containing lead methylammonium iodide and 0.5% benzoquinone in the photoelectric conversion layer of Example 2 and the photoelectric conversion element containing lead methylammonium iodide in the photoelectric conversion layer of Comparative Example 2, pseudo It is a graph which shows the time-dependent change of the photoelectric conversion efficiency at the time of continuous irradiation of sunlight. 5 is a graph showing changes over time in various device characteristics when continuous irradiation of pseudo sunlight is performed on the photoelectric conversion device containing lead methylammonium iodide and 0.5% benzoquinone of Example 2 in the photoelectric conversion layer. FIG. 3 is a graph showing current density-voltage characteristics of a photoelectric conversion element containing lead methylammonium iodide and 0.5% benzoquinone of Example 2 in a photoelectric conversion layer, measured by applying a voltage in the forward direction and the reverse direction. is there. Lead methylammonium iodide film containing benzoquinone, hydroquinone or tetracyanoquinodimethane as an additive, lead methylammonium iodide film containing no additive, and lead methylammonium iodide film containing no additive It is an emission spectrum of the laminated body which laminated | stacked _C60 layer. A photoelectric conversion element containing lead methylammonium iodide of Example 2 and 0.5% benzoquinone in a photoelectric conversion layer, a photoelectric conversion element containing lead methylammonium iodide of Comparative Example 2 in a photoelectric conversion layer, Comparative Example 3 Of the photoelectric conversion element containing lead methylammonium iodide and hydroquinone in the photoelectric conversion layer, and the current density of the photoelectric conversion element containing lead methylammonium iodide and tetracyanoquinodimethane of Comparative Example 4 in the photoelectric conversion layer- It is a graph which shows a voltage characteristic.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In addition, in this specification, the numerical range represented using "-" means the range which includes the numerical value described before and after "-" as a lower limit and an upper limit.

<Mixture>
The mixture of the present invention contains a quinone compound and a perovskite type compound.
When the perovskite type compound is left alone, it is gradually decomposed to release a metal halide, and the metal ion of the metal halide is reduced, so that a metal is produced. On the other hand, the mixture of the present invention contains the quinone compound together with the perovskite type compound, whereby the reduction of the metal ion liberated from the perovskite type compound is suppressed by the oxidative action of the quinone compound, and the generation of metal is suppressed. To be Therefore, in this mixture, excellent photoelectric conversion performance of the perovskite type compound can be stably obtained for a long period of time.
Below, each component which comprises this mixture is demonstrated in detail.

(Quinone compound)
The quinone-based compound accepts an electron and is relatively easily reduced to hydroquinone, as shown in the following reaction formula using 1,4-benzoquinone as an example. At that time, since the quinone-based compound robs an electron from the surroundings, it functions as an oxidant that suppresses the reduction of the metal ion released from the perovskite-type compound, and suppresses the formation of metal in the mixture to improve the performance of the perovskite-type compound. It has a stabilizing effect. In addition, since the quinone compound is particularly well compatible with water, it can prevent performance deterioration of the perovskite type compound even in a high humidity environment, and has an excellent property as an additive that it exhibits an effect even in a small amount. Moreover, the quinone-based compound does not adversely affect the crystal structure and light absorption characteristics of the perovskite-type compound and other characteristics of the photoelectric conversion element, and is extremely useful as a stabilizer for the perovskite-type compound.

The quinone-based compound has a quinone skeleton in which two hydrogen atoms of an aromatic hydrocarbon are respectively substituted with oxygen atoms to form a carbonyl group (-C (= O)-). The number of ring members in the quinone skeleton is not particularly limited, but it is preferably a 3- to 8-membered ring, and more preferably a 5- to 7-membered ring. The positions of the two carbonyl groups in the quinone skeleton are not particularly limited, and may be positions adjacent to each other or positions sandwiching one or more ring members. For example, in the case of a 6-membered quinone skeleton, the two carbonyl groups may be present at either the o-position or the p-position. The p-quinones have an advantage over the o-quinones in that decomposition is less likely to occur and are easier to handle, but any of them can function as an oxidizing agent that suppresses reduction of metal ions. The quinone compound may have a polycyclic condensed structure in which another ring is condensed in the quinone skeleton. The ring condensed to the quinone skeleton is not particularly limited, and may be any of aromatic hydrocarbon, aliphatic hydrocarbon ring, heteroaromatic ring, aliphatic heterocycle, etc., but aromatic hydrocarbon or aliphatic hydrocarbon ring It is preferably a hydrogen ring, and more preferably an aromatic hydrocarbon.
The quinone compound used in the present invention is preferably a compound represented by any of the following general formulas (1-1) to (1-3).

In formulas (1-1) to (1-3), R ^{1 to} R ⁴ each independently represent a hydrogen atom or a substituent.
The number of substituents in R ^{1 to} R ⁴ is not particularly limited, but is preferably 4 or less, more preferably 2 or less, and further preferably 0. The smaller the number of substituents of the quinone compound, the smaller the influence on the crystal structure and the light absorption characteristics of the perovskite type compound, and the better the compatibility with water. On the other hand, the oxidizing power of the quinone-based compound can be controlled by selecting the type and number of the substituents introduced into R ^{1 to} R ⁴ . Therefore, it is preferable to select the number of substituents among R ^{1 to} R ⁴ and the kind of the substituents to be adopted in consideration of the influence on the characteristics and the oxidizing power.

Examples of the substituent that R ^{1 to} R ⁴ may have include a halogen atom, a cyano group, a nitro group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and an alkyl-substituted amino group having 1 to 20 carbon atoms. , An aryl group having 6 to 40 carbon atoms, and the like. Among these specific examples, those substitutable with a substituent may be substituted with these substituents. Of these, an o- or p-oriented substituent such as an alkyl group, an alkoxy group, an alkyl-substituted amino group, or an aryl group tends to lower the oxidative power of a quinone-based compound, such as a cyano group or a nitro group. The m-oriented substituent tends to increase the oxidizing power of the quinone compound. The halogen atom has an o- or p-orientation, but its electron withdrawing property tends to increase the oxidizing power of the quinone compound.

R ¹ and R ² , and R ³ and R ⁴ may be bonded to each other to form a cyclic structure. The cyclic structure may be an aromatic ring or an alicyclic ring, may contain a hetero atom, and the cyclic structure may be a condensed ring having two or more rings. The hetero atom referred to herein is preferably selected from the group consisting of nitrogen atom, oxygen atom and sulfur atom. Examples of the formed cyclic structure include benzene ring, naphthalene ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, pyrrole ring, imidazole ring, pyrazole ring, triazole ring, imidazoline ring, oxazole ring, isoxazole ring, thiazole. Examples thereof include a ring, an isothiazole ring, a cyclohexadiene ring, a cyclohexene ring, a cyclopentaene ring, a cycloheptatriene ring, a cycloheptadiene ring and a cycloheptaene ring, which may be further substituted with a substituent. For specific examples of the substituents, the specific examples of the substituents that R ^{1 to} R ⁴ can take can be referred to. Among these cyclic structures, aromatic hydrocarbon or aliphatic hydrocarbon ring is preferable, and aromatic hydrocarbon ring is preferable, because the influence on the crystal structure and light absorption characteristics of the perovskite type compound is expected to be small. Is more preferable, and a benzene ring is still more preferable. Examples of the quinone compound in which the benzene ring is condensed to the quinone skeleton include substituted or unsubstituted anthraquinone, substituted or unsubstituted naphthoquinone, and the like.
The above quinone compounds may be used alone or in combination of two or more.

  The content of the quinone compound in the mixture is preferably 1/200 or more, and preferably 1/200 to 1/20, in terms of molar ratio with the perovskite compound ([quinone compound] / [perovskite compound]). It is preferable that it is 1/200 to 1/100, more preferably 1/200 to 1/150. This makes it possible to effectively suppress the reduction of metal ions released from the perovskite-type compound while suppressing the influence on the properties of the perovskite-type compound.

(Perovskite type compound)
The perovskite type compound has a function of being excited by light irradiation and generating holes and electrons (carriers) which are spatially separated.
The perovskite type compound is preferably an organic-inorganic perovskite type compound. The organic-inorganic perovskite-type compound is a compound having a perovskite-type structure composed of an organic cation A, a metal ion B, and a halogen ion X. By changing the organic group of the organic cation A, the metal ion B, or the halogen ion X, the structure is changed. And the physical properties can be precisely controlled. In addition, since it is possible to easily form a film by a solution coating method using abundant raw materials such as ammonium halides and metal halides, it is advantageous in reducing the cost of the photoelectric conversion element. Above all, it is preferable to use a lead iodide-based perovskite compound.

The organic / inorganic perovskite type compound is preferably a compound represented by the following general formula (2).
General formula (2)
ABX ₃

In the general formula (2), A represents an organic cation, B represents a divalent metal ion, and X represents a halogen ion. The three Xs may be the same as or different from each other.
The compound represented by the general formula (2) has a cubic unit cell, an organic cation A is arranged at each vertex of the cubic crystal, a metal ion B is arranged at the body center, and each face of the cubic crystal is arranged. A cubic perovskite structure in which halogen ions X are arranged in the center is formed. Here, an octahedron is formed by the inorganic skeleton of the metal ion B and the halogen ion X.

The organic cation represented by A is not particularly limited, but ammonium represented by the following general formula (4) is preferable.
General formula (4)
(R ¹⁰ ₄ N) ⁺

In formula (4), R ¹⁰ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and at least one of the four R ¹⁰ is a substituted or unsubstituted alkyl group. The number of substituted or unsubstituted alkyl groups among the four R ¹⁰ is preferably 1 or 2, and more preferably 1. That is, it is preferable that one of the four R ¹⁰ constituting ammonium is a substituent and the remaining is a hydrogen atom. When two or more of R ¹⁰ are substituted or unsubstituted alkyl groups, the plurality of substituted or unsubstituted alkyl groups may be the same or different, but are preferably the same. The number of carbon atoms of the substituted or unsubstituted alkyl group (the number of carbon atoms including the substituent in the case of a substituted alkyl group) is not particularly limited, but is preferably 1 to 20, and preferably 1 to 10. More preferably, it is even more preferably 1. That is, it is most preferable that one of the four R ¹⁰ constituting ammonium is a methyl group and the other is a hydrogen atom. Thereby, ammonium (R ¹⁰ ₄ N) ⁺ can be easily arranged at the apex of the cubic crystal of the perovskite structure. When R ¹⁰ is a substituted alkyl group, the substituent that substitutes the alkyl group is not particularly limited, and examples thereof include a phenyl group and a naphthalene group.
As the organic cation represented by A, cesium, formamidinium, or the like can be used in addition to ammonium.

The divalent metal ions represented by B include Cu ²⁺ , Ni ²⁺ , Mn ²⁺ , Fe ²⁺ , Co ²⁺ , Pd ²⁺ , Ge ²⁺ , Sn ²⁺ , Pb ²⁺ , Eu. ^{2+ and the} like can be mentioned, and Sn ²⁺ and Pb ²⁺ are preferable, and Pb ²⁺ is more preferable.
Examples of the halogen ion represented by X include F, Cl, Br, and I ions. The three halogen ions represented by X may be the same, or may be a combination of two or three types of halogen ions. Preferred is the case where all three X are the same halogen ion, and it is more preferred that all three X are I ⁻ .

Preferred specific examples of the organic-inorganic perovskite type compound represented by the general formula (2) include CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ PbCl ₃ , CH ₃ NH ₃ PbBr ₃ , CH ₃ NH ₃ SnI ₃ , and CH _{3. NH 3 SnCl 3, CH 3 NH} 3 SnBr 3 can be mentioned, preferably a CH ₃ NH ₃ PbI _3. However, the organic-inorganic perovskite type compound that can be used in the present invention is not limitedly interpreted by these compounds.

The organic-inorganic perovskite type compound is also preferably a compound represented by the following general formula (3).
General formula (3)
A ² ₂ A ¹ _n-1 B _n X _{3n + 1}

A ^{2 in the} general formula (3) represents an organic cation having a carbon number larger than that of A ¹ . B and X in the general formula (3) have the same meanings as B and X in the general formula (2), respectively, and A ^{1 in the} general formula (3) has the same meaning as A in the general formula (2). For the preferred ranges and specific examples of A ¹ , B and X in the general formula (3), the preferred ranges and specific examples of A, B and X in the general formula (2) can be referred to. Here, the two A ^{2 s} and the plurality of X s may be the same or different from each other. When a plurality of A ¹ and B are present, A ^1's and X's may be the same or different from each other.

The compound represented by the general formula (3) has a layered structure in which an inorganic layer composed of an octahedral inorganic skeleton B _n X _{3n + 1} and an organic layer composed of an organic cation A ² are alternately laminated. Form. n corresponds to the number of stacked octahedra in each inorganic layer and is an integer of 1 to 100. When n is 2 or more, the organic cation A ¹ is arranged at the position corresponding to the apex of the cubic crystal between the octahedra.

The organic cation represented by A ² is an organic cation having a carbon number larger than that of A ¹ , and is preferably ammonium represented by the following general formula (5).
General formula (5)
(R ¹¹ ₄ N) ⁺

In formula (5), R ¹¹ represents a hydrogen atom or a substituent, and at least one of the four R ¹¹ is a substituent having 2 or more carbon atoms. Of the four R ¹ , the number of substituents having 2 or more carbon atoms is preferably 1 or 2, and more preferably 1. That is, it is preferable that one of the four R ¹¹ constituting ammonium is a substituent having 2 or more carbon atoms and the remaining is a hydrogen atom. When two or more of R ¹¹ are substituents, the plurality of substituents may be the same or different. The substituent having 2 or more carbon atoms is not particularly limited, but an alkyl group, an aryl group,
Examples thereof include a phenyl group and a naphthyl group, and these substituents may be further substituted with an alkyl group, an aryl group, a phenyl group, a naphthyl group or the like. The alkyl group preferably has 2 to 30 carbon atoms, more preferably has 2 to 20 carbon atoms, and further preferably has 2 to 10 carbon atoms. In the aryl group, it is preferably 6 to 30, more preferably 6 to 20, and further preferably 6 to 10. The thickness of the organic layer is controlled according to the major axis length of the substituent represented by R ¹¹ (for example, the chain length of the alkyl group), thereby controlling the characteristics of the functional layer formed by this mixture. be able to.

As the organic cation represented by A ² , cesium, formamidinium, and the like can be used in addition to ammonium.

Specific preferred examples of the organic-inorganic perovskite type compound represented by the general formula (3) include [CH ₃ (CH ₂ ) _n NH ₃ )] ₂ PbI ₄ (n = _{2 to} 17) and (C ₄ H ₉ C _{2 H 4 NH 3) 2 PbI 4} , (CH 3 (CH 2) n (CH 3) CHNH 3) 2 PbI 4 [n = 5~8], (C 6 H 5 C 2 H 4 NH 3) 2 PbI 4 , mention may be made of _{(C 10 H 7 CH 2 NH} 3) 2 PbI 4 and _{(C 6 H 5 C 2 H} 4 NH 3) 2 PbBr 4 or the like. However, the organic-inorganic perovskite type compound that can be used in the present invention is not limitedly interpreted by these compounds.

Among the organic-inorganic perovskite type compounds mentioned above, the preferable ones are the compounds represented by the general formula (2), in which B is Pb ²⁺ and X is I ⁻ (lead iodide-based compound). Perovskites) are preferred, and CH ₃ NH ₃ PbI ₃ is most preferred.
Further, the perovskite type compounds may be used alone or in combination of two or more.

  The mixture of the present invention may be composed of only the perovskite type compound and the quinone compound, or may contain other light sensitive components and additives.

<Functional layer>
The functional layer of the present invention is formed by layering the mixture of the present invention. This functional layer can be formed by forming a film containing a mixture containing the perovskite type compound of the present invention and a quinone compound.
The film forming method is not particularly limited, and may be a vapor phase process such as a vacuum vapor deposition method or a solution coating method, but the solution coating method can be used because a film can be formed in a short time with a simple apparatus. Preferably there is. The method of forming the functional layer by the solution coating method will be described below.
First, a coating solution (a solution containing the mixture of the present invention) containing a perovskite type compound and a quinone compound is prepared. The coating solution can be prepared, for example, by reacting an ammonium halide and a metal halide in a solvent to obtain a precursor of an organic-inorganic perovskite type compound, and then adding and mixing a quinone compound. . Here, the preferable range and specific examples of the organic group and the halogen ion bonded to the nitrogen atom of the ammonium halide, the halogen ion and the metal ion of the metal halide are represented by R ¹⁰ of the general formula (4) in the above <mixture>. Alternatively, preferred examples and specific examples of R ^{11 in the} general formula (5), X and B in the general formula (2) and the general formula (3) can be referred to. For the preferable range and specific examples of the quinone compound, the preferable range and specific examples of the quinone compound in the above <mixture> can be referred to.
The coating method of the coating solution is not particularly limited, and conventionally known coating methods such as a gravure coating method, a bar coating method, a printing method, a spray method, a spin coating method, a dip method, and a die coating method can be used.

The solvent for the coating solution is not particularly limited as long as it can dissolve the perovskite type compound and the quinone compound. Specifically, esters (methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate, etc.), ketones (γ-butyrolactone, N-methyl-2-pyrrolidone, acetone) , Dimethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, etc., ethers (diethyl ether, methyl-tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane , 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, anisole, phenetole, etc.), alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butane) Nol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol, methoxypropanol, diacetone alcohol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2, 2,3,3-Tetrafluoro-1-propanol, etc., glycol ethers (cellosolves) (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, triethylene glycol dimethyl ether, etc. ), Amide solvents (N, N-dimethylformamide, acetamide, N, N-dimethylacetamide, etc.), nitrile solvents (acetonitrile, isobutyronitrile, propionitrile, metho Toxiacetonitrile etc.), carboat type agents (ethylene carbonate, propylene carbonate etc.), halogenated hydrocarbons (methylene chloride, dichloromethane, chloroform etc.), hydrocarbons (n-pentane, cyclohexane, n-hexane, benzene, toluene, xylene etc.) ), Dimethyl sulfoxide and the like. In addition, it may have two or more of any of functional groups of ester, ketone, ether, and alcohol (that is, -O-, -CO-, -COO-, -OH). The hydrogen atom in the hydrocarbon moiety of the esters, ketones, ethers and alcohols may be replaced with a halogen atom (especially fluorine atom).
The functional layer of the present invention can be suitably used as a photoelectric conversion layer of a photoelectric conversion element and can also be used as a light emitting layer.

<Photoelectric conversion element>
Next, the photoelectric conversion element of the present invention will be described.
The photoelectric conversion element of the present invention has a layer containing a quinone compound and a perovskite compound. For the description and preferred ranges and specific examples of the quinone compound and perovskite type compound, the description and preferred ranges and specific examples of the quinone compound and perovskite type compound in the above <mixture> can be referred to.
The perovskite-type compound is excited by light irradiation and efficiently generates spatially separated holes and electrons (carriers), and thus can effectively function as a material for the photoelectric conversion layer. On the other hand, when the perovskite type compound is left alone, it gradually decomposes to release the metal halide, and the metal ion of the metal halide is reduced. As a result, the metal accumulation phenomenon is observed. The metal accumulated in the photoelectric conversion layer traps carriers generated from the perovskite-type compound, and thus becomes a factor that deteriorates device characteristics such as photoelectric conversion efficiency with time. On the other hand, the photoelectric conversion device of the present invention includes a quinone compound in the layer containing the perovskite compound, so that the quinone compound functions as an oxidant that suppresses the reduction of metal ions released from the perovskite compound. The generation of metal is suppressed. Therefore, this photoelectric conversion element is provided with good element characteristics even after a long period of time since its manufacture, and even when the environment in which it is used is high humidity, in which the carrier is efficiently collected by the electrode. be able to. As a result, this photoelectric conversion element has a longer life than a photoelectric conversion element that does not include a quinone compound, and stable driving can be realized even in a high humidity environment.

The photoelectric conversion element of the present invention preferably has a structure in which at least a transparent electrode and a counter electrode, and a power generation layer is formed between the transparent electrode and the counter electrode. The power generation layer includes at least a photoelectric conversion layer, may be composed of only a photoelectric conversion layer, or may have one or more functional layers in addition to the photoelectric conversion layer. Examples of such other functional layer include a hole transport layer, an electron block layer, an electron transport layer, a hole block layer, and the like. A specific example of the structure of the photoelectric conversion element is shown in FIG. In FIG. 1, 1 is a transparent substrate, 2 is a transparent electrode, 3 is a hole transport layer, 4 is a photoelectric conversion layer, 5 is an electron transport layer, and 6 is a counter electrode. In the configuration of FIG. 1, the transparent electrode 1 functions as a positive electrode that collects holes, and the counter electrode 6 functions as a negative electrode that collects electrons. Further, the photoelectric conversion element may be one in which the hole transport layer 3 and the electron transport layer 5 are arranged at a position opposite to the positional relationship shown in FIG. That is, the transparent substrate 1, the transparent electrode 2, the electron transport layer 5, the photoelectric conversion layer 4, the hole transport layer 3, and the counter electrode 6 may be laminated in this order. In this case, the transparent electrode 1 functions as a negative electrode that collects electrons, and the counter electrode 6 functions as a positive electrode that collects holes.
Each member and each layer of the photoelectric conversion element will be described below.

(Transparent substrate)
The photoelectric conversion element of the present invention is preferably supported on a transparent substrate. The transparent substrate is not particularly limited as long as it is conventionally used for photoelectric conversion elements, and for example, a substrate made of glass, transparent plastic, quartz or the like can be used. Examples of transparent plastics include polyesters such as polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), polycarbonates, polyolefins, polyimides, Teflon (registered trademark), and the like.

(Transparent electrode)
As the transparent electrode in the photoelectric conversion element, those using an electrically conductive inorganic compound, an electrically conductive metal oxide, an electrically conductive polymer and a mixture thereof as an electrode material are preferably used. Specific examples of such electrode materials include conductive inorganic compounds such as CuI, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide (SnO ₂ ), indium zinc oxide (IZO), Conductive metal oxides such as gallium-doped zinc oxide, aluminum-doped zinc oxide (AZO), zinc oxide (ZnO), and niobium-doped titanium oxide, conductive materials such as polyacetylene-based, polypyrrole-based, polythiophene-based, and polyphenylene vinylene-based Polymers can be mentioned. Alternatively, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous transparent conductive film may be used. The transparent electrode may be formed into a thin film by a method such as vapor deposition or sputtering of these electrode materials, and a pattern of a desired shape may be formed by a photolithography method. The pattern may be formed through a mask. Alternatively, when a coatable material such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can be used. The surface resistance of the transparent conductive film is preferably 15Ω / □ or less, more preferably 5Ω / □ or less. Further, the film thickness depends on the material, but is usually selected in the range of 0.01 to 10.0 μm, preferably 0.1 to 1.0 μm.

(Counter electrode)
As the counter electrode, in addition to the electrode materials exemplified as the transparent electrode, those having a metal, alloy, carbon material or a mixture thereof as an electrode material are used.
Specific examples of metals and alloys used as the electrode material include metals and alloys such as aluminum, gold, silver, platinum, copper, tungsten, molybdenum, and titanium. The counter electrode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The surface resistance of the counter electrode is preferably 15 Ω / □ or less, more preferably 5 Ω / □ or less. The film thickness of the counter electrode is usually selected from the range of 0.01 to 2.0 μm.

(Photoelectric conversion layer)
The photoelectric conversion layer contains a quinone compound and a perovskite type compound. When the photoelectric conversion layer is irradiated with light from the transparent substrate side, the perovskite compound is photoexcited to generate spatially separated holes and electrons (carriers). Among these carriers, holes diffuse to the positive hole transport layer side and are taken out to the positive electrode, and electrons diffuse to the positive electron transport layer side to be taken out to the negative electrode, so that a potential difference (electromotive force) is generated between the electrodes.
Here, since the photoelectric conversion layer contains the quinone-based compound, reduction of metal ions derived from the perovskite type compound and metal accumulation can be suppressed. Therefore, the generated carriers are hard to be trapped in the photoelectric conversion layer, and the carriers can be efficiently taken out to each electrode.
For the content of the quinone compound in the photoelectric conversion layer, the content of the quinone compound in the above mixture can be referred to.
The thickness of the photoelectric conversion layer is preferably 10 to 1000 nm, more preferably 100 to 500 nm, and further preferably 200 to 400 nm. Thereby, the photoelectric conversion element can be prevented from becoming too thick, and sufficient power generation characteristics can be obtained.

(Hole transport layer)
The hole transport layer is made of a hole transport material having a function of transporting holes injected from the photoelectric conversion layer to the positive electrode side, and a single layer or a plurality of layers can be provided. In addition to the function of transporting holes, the hole transport material may have hole injection and electron barrier properties.
Examples of the hole transport material include spiro-OMeTAD (2,2 ', 7,7'-tetrakis- (N, N-di-p-methoxyphenylamine) 9,9'-spirobifluorene)) and poly (3 , 4-ethylenedioxythiophene): poly (4-styrenesulfonate) (PEDOT: PSS), P3HT (poly (3-hexylthiophene)), PCPDTBT (poly [2,1,3-benzothiadiazole-4,7-) Diyl [4,4-bis (2-ethylhexyl) -4H-cyclopenta [2,1-b: 3,4-b '] dithiophene-2,6-diyl]]), PVK (poly (N-vinylcarbazole)) ), HTM-TFSI (1-hexyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide), Li-TFSI (lithium bis (trifluoro). Examples thereof include spiro-OMeTAD, P3HT, PCPDTBT, and PVK, and more preferably spiro-OMeTAD. Further, as hole transport materials, thiophenyl, phenylenyl, dithiazolyl, benzothiazolyl, diketopyrrolopyrrolyl, ethoxydithiophenyl, amino, triphenylamino, carbozolyl, ethylenedioxythiophenyl, dioxythiophenyl and fluorenyl are selected. It is also possible to use an organic compound, polymer or copolymer having one or more selected groups, and also an inorganic hole transport material such as CuI, CuBr, CuSCN, Cu2O, CuO, CIS.
The thickness of the hole transport layer is not particularly limited, but is preferably about 0.01 to 0.5 μm.

(Electron transport layer)
The electron transport layer is made of a material having a function of transporting electrons injected from the photoelectric conversion layer to the negative electrode side, and a single layer or a plurality of layers can be provided. The electron transport material may have a function of blocking holes in addition to a function of transporting electrons.
Examples of the electron transport material include fullerene, perylene, fullerene, or a derivative of perylene, poly {[N, N'-bis (2-octyldodecyl) -naphthalene-1,4,5,8-bis (dicarboximide) -2. , 6-diyl] -alt-5,50- (2,20-bithiophene)} (P (NDI2OD-T2)) and the like, and various electrolytes can also be used.
As the electron transporting material, metal oxides such as TiO ₂ , WO ₃ , ZnO, Nb ₂ O ₅ , Ta ₂ O ₅ , and SrTiO ₃ and donor-added metal oxides obtained by adding a donor to these metal oxides are used. May be. When TiO ₂ is used, its crystal form is preferably anatase type. The metal oxide used for the electron transport material preferably has a porous structure, and more preferably has a porous structure in which the pore size is nano-order. As a result, the surface area of the electron transport layer itself increases, and when the photoelectric conversion layer is formed thereon, the surface area of the photoelectric conversion layer at the interface with the electron transport layer also increases. As a result, the efficiency of injecting electrons from the photoelectric conversion layer into the electron transport layer is increased, and the photoelectric conversion efficiency can be improved. Examples of the porous structure include a structure in which granular bodies, linear bodies (linear bodies: needle-shaped, tube-shaped, column-shaped, etc.) are aggregated to form a porous structure as a whole. The porous structure does not need to extend over the entire electron transport layer, and for example, the negative electrode side portion may have a smooth structure and the photoelectric conversion layer side portion may have a porous structure. When the electron transport layer has a porous structure with the expectation of increasing the surface area of the photoelectric conversion layer, it is preferable to dispose the electron transport layer on the transparent electrode side of the photoelectric conversion layer. Thereby, after the electron transport layer having a porous structure is formed, the manufacturing procedure is such that the photoelectric conversion layer is formed thereon. Therefore, the photoelectric conversion layer reflecting the surface shape of the electron transport layer, that is, the photoelectric conversion layer having a large surface area is formed. Can be easily obtained.
The thickness of the electron transport layer is not particularly limited, but is preferably about 0.01 to 0.5 μm.

(Hole blocking layer)
The hole blocking layer is provided between the electron transport layer and the negative electrode as needed. The hole blocking layer has a function of an electron transport layer in a broad sense. The hole blocking layer has a role of blocking the arrival of holes at the negative electrode while transporting electrons to the negative electrode, and thereby a large electromotive force can be generated between the transparent electrode and the counter electrode. As the material of the hole blocking layer, one having a HOMO level deeper than the HOMO level of the material forming the electron transporting layer can be selected and used from the materials of the electron transporting layer.

(Electronic block layer)
The electron block layer is provided between the hole transport layer and the positive electrode as needed. The electron blocking layer has a function of transporting holes in a broad sense. The electron blocking layer has a role of blocking the electrons from reaching the positive electrode while transporting the holes to the positive electrode, whereby a large electromotive force can be generated between the transparent electrode and the counter electrode. As the material of the electron block layer, one having a LUMO level shallower than the LUMO level of the material forming the hole transport layer can be selected and used from the materials of the hole transport layer.

  When manufacturing the above photoelectric conversion element, the method for forming each functional layer constituting the power generation layer is not particularly limited, and may be formed by either a dry process or a wet process.

  When this photoelectric conversion element is irradiated with light such as sunlight from the transparent substrate side, the perovskite type compound contained in the photoelectric conversion layer is excited to generate carriers. Of the carriers, holes are transported to the positive electrode side and taken out to the positive electrode, and electrons are transported to the negative electrode side and taken out to the negative electrode, so that electromotive force is generated between the positive electrode and the negative electrode. A current flowing from the positive electrode to the negative electrode can be obtained by connecting a conductor between the positive electrode and the negative electrode where the electromotive force is generated.

  The photoelectric conversion element of the present invention may be used as a single element or may be of a tandem type in which a plurality of elements are laminated. By adopting the tandem type, high conversion efficiency can be realized. Further, by stacking elements having different characteristics, the characteristics of the entire stacked elements can be precisely controlled, and the optimum characteristics suitable for the application can be realized.

The features of the present invention will be described more specifically below with reference to Examples and Comparative Examples. Materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following specific examples.
The organic-inorganic perovskite layer was evaluated using an X-ray diffractometer [λ = 1.54Å (CuKα)] (manufactured by Rigaku Corporation: Ultima IV) and a spectrofluorometer (manufactured by JASCO Corporation: FP-6500). The photoelectric conversion element was evaluated using a solar simulator (XIL-05B100KP manufactured by Celic), a measurement system (OSA-11 manufactured by System Engineer), and a source meter (2400 series manufactured by Keithley).
Further, in each of the following examples, the concentration of benzoquinone in the perovskite layer (photoelectric conversion layer) is a molar ratio [benzoquinone] / [lead methylammonium iodide] or a molar percentage ([benzoquinone] / [ Lead methyl iodide]] × 100 (%).

<Production and evaluation of photoelectric conversion element>
(Example 1)
A glass substrate having a positive electrode made of indium tin oxide (ITO) and having a film thickness of 120 nm was prepared. PEDOT: PSS was spin-coated on this ITO at 3000 rpm for 30 seconds to form a coating film, which was then heated on a hot plate at 160 ° C. for 10 minutes to form a PEDOT: PSS layer having a thickness of 50 nm.
Next, a perovskite (CH ₃ NH ₃ PbI ₃ ) layer was formed as a photoelectric conversion layer in a nitrogen atmosphere glove box. First, PbI ₂ and CH ₃ NH ₃ I were dissolved in dimethyl sulfoxide at a molar ratio of 1: 1 and reacted with stirring to synthesize a precursor of lead methylammonium iodide (CH ₃ NH ₃ PbI ₃ ). Benzoquinone was added to this reaction solution, and the solution was prepared by stirring. The content of lead methylammonium iodide in the solution was 620 mg / mL, and the addition amount of benzoquinone was 1/1000 in terms of molar ratio to lead methylammonium iodide. This solution was spin-coated on the PEDOT: PSS layer at 4000 rpm for 30 seconds to form a precursor layer. The precursor layer was heated on a hot plate at 60 ° C. for 15 minutes, followed by heating at 100 ° C. for 30 minutes. Through the above steps, a perovskite layer having a thickness of 0.3 μm was formed and used as a photoelectric conversion layer.
Then, a chlorobenzene solution prepared by dissolving [70] PCBM at a concentration of 20 mg / mL was spin-coated on the perovskite layer in a nitrogen atmosphere glove box at 1000 rpm for 30 seconds, and then on a hot plate at 100 ° C. for 30 seconds. A [70] PCBM layer was formed by heating for a minute. Then, LiF is formed to a thickness of 0.8 nm on the [70] PCBM layer by a vacuum evaporation method with a vacuum degree of 10 ⁻⁴ Pa, and Al is formed to a thickness of 100 nm on the LiF. Thus, a cathode was formed and a photoelectric conversion element was obtained.
Further, when the perovskite layer was formed, the same procedure as above was performed except that the addition amount of benzoquinone to the solution was changed to 1/200, 1/100 or 1/20 in terms of molar ratio to lead methylammonium iodide. Various photoelectric conversion elements were produced.

(Comparative Example 1)
A photoelectric conversion element was produced in the same manner as in Example 1 except that benzoquinone was not added to the solution for forming the perovskite layer.
The X-ray diffraction spectrum of the photoelectric conversion layer (perovskite layer) formed in Example 1 and Comparative Example 1 is shown in FIG. 2, and the light absorption spectrum is shown in FIG. FIG. 4 shows the device characteristics of the photoelectric conversion devices produced in Example 1 and Comparative Example 1 immediately after production, and white light (light irradiation intensity: 100 mW / cm ² ) was obtained under the conditions of temperature 298K and humidity 50%. FIG. 5 shows the change over time in the photoelectric conversion characteristics when continuously irradiated with. In the drawings, "BQ" represents benzoquinone, "MAPbI _3" in FIG. 2 represents a lead iodide methyl ammonium.
2 and 3, almost no difference was observed in the X-ray diffraction spectrum and the light absorption spectrum between the photoelectric conversion layer containing benzoquinone and the photoelectric conversion layer containing no benzoquinone. From this, it was confirmed that benzoquinone did not affect the crystal structure and light absorption characteristics of the perovskite type compound.
From FIG. 4, it was found that the photoelectric conversion element in which benzoquinone was added at a molar ratio of 1/1000 improved the photoelectric conversion efficiency by about 20% as compared with the photoelectric conversion element in which benzoquinone was not added. Further, from FIG. 5, it is confirmed that the photoelectric conversion element to which benzoquinone is added has a significantly lower rate of decrease in photoelectric conversion efficiency than the photoelectric conversion element to which benzoquinone is not added, and deterioration of characteristics over time is suppressed by the addition of benzoquinone. Was done. Further, the effect of suppressing the deterioration with time is particularly remarkably exhibited in the element group to which benzoquinone is added at a molar ratio of 1/200 or more. From this, it was found that the addition amount of benzoquinone is preferably 1/200 or more in terms of molar ratio to the perovskite type compound. In addition, in FIG. 4, when the addition amount of benzoquinone exceeds 1/100, there is a tendency that the initial characteristic value becomes lower than that in the case of no addition. However, as shown in Example 2 below, by changing the element configuration, it is possible to shift the density at which the element characteristics are sloping downward to the high density side. As a result, even in the range where the amount of benzoquinone added exceeds 1/100 (0.1%), excellent device characteristics can be obtained which are superior to the case where no benzoquinone is added.

(Example 2)
A glass substrate having a positive electrode made of indium tin oxide (ITO) and having a thickness of 150 nm was prepared. A PEDOT: PSS layer having a thickness of 50 nm was formed on the ITO by spin coating PEDOT: PSS at 3000 rpm for 45 seconds to form a coating film, which was then heated on a hot plate at 160 ° C. for 10 minutes.
Next, a perovskite (CH ₃ NH ₃ PbI ₃ ) layer was formed as a photoelectric conversion layer in a nitrogen atmosphere glove box. First, PbI ₂ and CH ₃ NH ₃ I were dissolved in a mixed solvent of γ-butyrolactone and dimethylformamide (volume ratio 4: 6) at a molar ratio of 1: 1 and reacted by stirring at 60 ° C. for 12 hours. Then, a precursor of lead methylammonium iodide (CH ₃ NH ₃ PbI ₃ ) was obtained. Benzoquinone was added to this reaction solution, and the solution was prepared by stirring. The concentration of lead methylammonium iodide in the solution was 1.2 M, and the amount of benzoquinone added was 1/1000 (0.1%) in terms of molar ratio to lead methylammonium iodide. This solution was spin-coated on the PEDOT: PSS layer at 4000 rpm for 30 seconds to form a precursor layer. During the spin coating, 0.3 mL of toluene was dropped on the precursor layer. The precursor layer was heated on a hot plate at 60 ° C. for 15 minutes, followed by heating at 100 ° C. for 30 minutes. Through the above steps, a perovskite layer having a thickness of 350 nm was formed and used as a photoelectric conversion layer.
Next, C ₆₀ was formed to a thickness of 30 nm on the perovskite layer by a vacuum evaporation method under the condition of a vacuum degree of 10 ⁻⁴ Pa, BCP was formed to a thickness of 10 nm, and Au was further formed thereon. The negative electrode was formed by forming it to a thickness of 100 nm to obtain a photoelectric conversion element.
Furthermore, when the perovskite layer is formed, the amount of benzoquinone added to the solution is 1/200 (0.5%), 1/100 (1%) or 1/20 (5%) in terms of molar ratio to lead methylammonium iodide. Various photoelectric conversion elements were prepared in the same manner as above except that the photoelectric conversion element was changed to (1).

(Comparative example 2)
A photoelectric conversion element was produced in the same manner as in Example 2 except that benzoquinone was not added to the solution for forming the perovskite layer.

(Comparative example 3)
When forming the perovskite layer, photoelectric conversion was performed in the same manner as in Example 2 except that hydroquinone (HQ) was added at a molar percentage of 0.5% with respect to lead methylammonium iodide instead of adding benzoquinone to the solution. A device was produced.

(Comparative example 4)
Example 2 was repeated except that tetracyanoquinodimethane (TCNQ) was added in a molar percentage of 0.5% with respect to lead methylammonium iodide instead of adding benzoquinone to the solution when forming the perovskite layer. A photoelectric conversion element was produced in the same manner as in.
For the photoelectric conversion elements produced in Example 2 and Comparative Example 2, immediately after the production, the element characteristics measured under irradiation of pseudo sunlight with a xenon lamp (AM 1.5 G, light irradiation intensity: 100 mW / cm ² ) are shown in FIG. Shown in. The measured device characteristics are a fill factor, an open circuit voltage Voc, a short circuit current Jsc, and a photoelectric conversion efficiency η. Further, FIG. 7 shows a change with time in photoelectric conversion efficiency when white light (light irradiation intensity: 100 mW / cm ² ) was continuously irradiated under the condition of a temperature of 298 K and a humidity of 50%. Further, among the photoelectric conversion elements manufactured in Example 2, the photoelectric conversion element in which benzoquinone was added to the perovskite layer in an amount of 0.5% was simulated sunlight (AM1.5G, light) using a xenon lamp without using an ultraviolet cut filter. FIG. 8 shows the changes over time in the photoelectric conversion efficiency when continuously irradiating the irradiation intensity: 100 mW / cm ² ), and FIG. 9 shows the changes over time in the characteristics of various elements. Further, FIG. 10 shows current density-voltage characteristics measured by applying a voltage in the forward direction and the reverse direction. The vertical axis in FIGS. 7 and 8 represents the photoelectric conversion efficiency, and the numerical value is a relative value when the initial photoelectric conversion efficiency is 1. The vertical axis in FIG. 9 represents the measured values of the short circuit current Js, the open circuit voltage Voc, the fill factor FF, and the photoelectric conversion efficiency η. In each figure, "BQ" represents benzoquinone. Further, in the change over time of the photoelectric conversion efficiency shown in FIG. 7, time T80 is shown in Table 1 until the photoelectric conversion efficiency reaches 80% of the initial value, and in the change over time of the photoelectric conversion efficiency shown in FIG. Table 2 shows the time T80 until the efficiency reaches 80% of the initial value.

It can be seen from FIG. 6 that the device characteristics of the photoelectric conversion device are remarkably improved by adding benzoquinone to the perovskite layer. For example, the photoelectric conversion efficiency η of the photoelectric conversion element added with 0.5% of benzoquinone is 14.69%, which is equal to the photoelectric conversion efficiency η (10.73%) of the photoelectric conversion element without benzoquinone (Comparative Example 2). It is significantly improved. The effect of improving the photoelectric conversion efficiency seen in FIG. 6 and FIG. 4 is that the crystal formation rate of the perovskite layer was slowed by the addition of benzoquinone, and thus the perovskite layer excellent in morphology and crystallinity was formed. It is speculated that this is because the transfer of electrons from lead methylammonium iodide to benzoquinone suppressed the loss due to recombination of charges. However, when the concentration of benzoquinone was increased, the device characteristics tended to decrease to a right from a certain concentration. From this result, the addition amount of the quinone-based compound to the perovskite layer is preferably 0.05 to 4%, more preferably 0.1 to 3%, and more preferably 0.1 to 3% in terms of molar percentage with respect to the perovskite type compound. It was shown that it is more preferable that it is 2 to 1%.
Next, regarding deterioration with time of the photoelectric conversion efficiency under continuous light irradiation, from FIGS. 7 to 9 and Tables 1 and 2, by adding benzoquinone to the perovskite layer, as compared with the photoelectric conversion element without benzoquinone addition, It can be seen that the deterioration with time is effectively suppressed. In particular, looking at FIG. 9 (change with time under irradiation of pseudo sunlight without using an ultraviolet cut filter), in the photoelectric conversion element to which benzoquinone (0.5%) was added, the initial 90% was observed even after 2000 hours had elapsed. The photoelectric conversion efficiency of is maintained. From this, it could be confirmed that the quinone-based compound is extremely useful as an additive that extends the life of the photoelectric conversion element. However, as shown in Table 1, when the benzoquinone concentration was increased, the element life T80 tended to be shortened from a certain concentration. From this result, from the viewpoint of device life, the addition amount of the quinone-based compound is preferably 0.05 to 0.8 mol% and more preferably 0.1 to 0.7 mol% in terms of mol percentage with respect to the perovskite type compound. Was more preferable, and 0.1 to 0.5 mol% was more preferable.
FIG. 10 is an examination of the hysteresis characteristics of a photoelectric conversion element in which 0.5% of benzoquinone is added to the perovskite layer. From FIG. 10, it was found that in this photoelectric conversion element, almost the same current density-voltage curve was obtained in the forward scan and the reverse scan, and the hysteresis was extremely small.
FIG. 11 shows a lead methylammonium iodide film containing 0.5% by mole of benzoquinone, hydroquinone or tetracyanoquinodimethane, a lead methylammonium iodide film containing no additive, and an additive. FIG. 12 shows an emission spectrum of a laminate obtained by laminating a C ₆₀ layer on a film of lead methylammonium iodide which is not present. FIG. 12 shows that, in the photoelectric conversion element prepared in Example 2, 0.5% of benzoquinone was added to the perovskite layer. The current density-voltage characteristics of the photoelectric conversion element and the photoelectric conversion elements produced in Comparative Examples 2 to 4 are shown. In FIGS. 11 and 12 and Table 3 below, “BQ” represents a film or photoelectric conversion element (Example 2) to which benzoquinone was added, and “no additive” was a film or photoelectric conversion element (to which no additive was added). Comparative Example 2), "HQ" represents a film or photoelectric conversion element added with hydroquinone (Comparative Example 3), and "TCNQ" represents a film or photoelectric conversion element added with tetracyanoquinodimethane (Comparative Example 4). And C ₆₀ represents a laminate in which a C ₆₀ layer is laminated on a film containing no additive. In addition, Table 3 shows the device characteristics of the photoelectric conversion device in which 0.5 mol% of benzoquinone was added to the perovskite layer (Example 2) and the photoelectric conversion devices produced in Comparative Examples 2 to 4. In the following description, benzoquinone, hydroquinone, and tetracyanoquinodimethane are also collectively referred to as “additives”.

It can be seen from FIG. 11 that the emission peak is observed in the film to which the additive is not added, but such emission peak disappears in the film to which benzoquinone, hydroquinone or tetracyanoquinodimethane is added. The disappearance of this peak suggests that holes or electrons generated in lead methylammonium iodide upon irradiation with light were transferred to the additive. From this, it was confirmed that benzoquinone, hydroquinone, or tetracyanoquinodimethane has a common function in that it can receive the charge generated by lead methylammonium iodide.
Next, referring to FIG. 12 and Table 3, the device characteristics of the photoelectric conversion device of Example 2 to which benzoquinone was added were remarkably improved as compared with the photoelectric conversion device of Comparative Example 2 to which no additive was added. You can see that On the other hand, the photoelectric conversion element of Comparative Example 4 to which tetracyanoquinodimethane was added had a lower photoelectric conversion efficiency η than the photoelectric conversion element of Comparative Example 2 to which the additive was not added. It is considered that this is because tetracyanoquinodimethane has a LUMO deeper than that of the C ₆₀ layer, thereby trapping electrons and functioning as a recombination center of charges, and the electron extraction efficiency at the cathode is lowered. On the other hand, the device characteristics of the photoelectric conversion device of Comparative Example 3 containing hydroquinone are equivalent to the device properties of the photoelectric conversion device of Comparative Example 2 containing no additive, and hydroquinone does not affect the device characteristics. It has been suggested. From the above, it was found that among these additives, benzoquinone is suitable as the additive to be added to the perovskite layer.

  The photoelectric conversion element of the present invention can be used as a photoelectric conversion element (solar cell) that converts sunlight into electric energy, has a long life, and can be stably driven even in a high humidity environment. Further, this photoelectric conversion device can be manufactured by using the solution coating method, and the manufacturing cost can be kept low. Therefore, according to the present invention, it is possible to greatly contribute to the spread of solar cells, and the industrial applicability is extremely high.

1 Substrate 2 Positive Electrode 3 Hole Transport Layer 4 Photoelectric Conversion Layer 5 Electron Transport Layer 6 Negative Electrode

Claims (17)

A mixture containing a compound represented by the following general formula (1-1) or the following general formula (1-3) and an organic-inorganic perovskite type compound ,
The content of the compound represented by the general formula (1-1) or the general formula (1-3) is a molar ratio ([general formula (1-1) or general formula (1-1) The compound represented by 1-3)] / [organic / inorganic perovskite type compound]) is 1/200 to 1/20 .

(In the general formulas (1-1) and (1-3), R ^{1 to} R ⁴ each independently represent a hydrogen atom, a cyano group, a nitro group or a halogen atom. R ¹ and R ² , R ³ and R ^{4 s} may be bonded to each other to form an aromatic hydrocarbon ring.) The mixture according to claim 1 , wherein R ^{1 to} R ^{4 in the} general formula (1-1) or the general formula (1-3) are hydrogen atoms. The organic-inorganic perovskite compound mixture according to claim 1 or 2 is a lead iodide based perovskite. The mixture according to claim 1 or 2 , wherein the organic-inorganic perovskite type compound is a compound represented by the following general formula (2) or the following general formula (3).
General formula (2)
ABX ₃
[In the general formula (2), A represents an organic cation, B represents a divalent metal ion, and X represents a halogen ion. The three Xs may be the same or different from each other]
General formula (3)
A ² ₂ A ¹ _n-1 B _n X _{3n + 1}
[In the general formula (3), A ¹ represents an organic cation, and A ² represents an organic cation having a carbon number larger than that of the organic cation represented by A ¹ . B represents a divalent metal ion, and X represents a halogen ion. n is an integer of 1-10. The two A ^{2 s} and the plurality of X s may be the same or different from each other. When a plurality of A ¹ and B are present, A ^1's and X's may be the same or different from each other. ] The mixture according to claim 4 , wherein A in the general formula (2) and A ¹ in the general formula (3) are ammonium represented by the following general formula (4).
General formula (4)
(R ¹⁰ ₄ N) ⁺
[In the general formula (4), R ¹⁰ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and at least one of the four R ¹⁰ is a substituted or unsubstituted alkyl group. ] The mixture according to claim 5 , wherein R ^{10 in the} general formula (4) is a methyl group. The mixture according to any one of claims 4 to 6 , wherein A ² in the general formula (3) is ammonium represented by the following general formula (5).
General formula (5)
(R ¹¹ ₄ N) ⁺
[In General Formula (5), R ¹¹ represents a hydrogen atom or a substituent, and at least one of the four R ¹¹ is a substituent having 2 or more carbon atoms. ] The mixture according to any one of claims 4 to 7 , wherein B in the general formula (2) and the general formula (3) is Pb ²⁺ . The mixture according to claim 4 , wherein X in the general formula (2) or the general formula (3) is I ⁻ . The mixture according to any one of claims 4 to 9 , wherein the organic-inorganic perovskite type compound is a compound represented by the general formula (2). Functional layer comprising a mixture according to any one of claims 1 to 10. The functional layer according to claim 11 , which is a photoelectric conversion layer. A photoelectric conversion element comprising a transparent electrode and a counter electrode, and a layer containing a compound represented by the following general formula (1-1) or the following general formula (1-3) and an organic-inorganic perovskite type compound ,
A photoelectric conversion element , wherein the counter electrode is made of a metal, an alloy, a carbon material or a mixture thereof .

(In the general formulas (1-1) and (1-3), R ^{1 to} R ⁴ each independently represent a hydrogen atom, a cyano group, a nitro group or a halogen atom. R ¹ and R ² , R ³ and R ^{4 s} may be bonded to each other to form an aromatic hydrocarbon ring.) A layer comprising a compound represented by the general formula (1-1) or the general formula (1-3) and an organic-inorganic perovskite type compound, comprising the mixture according to any one of claims 1 to 10. Item 13. The photoelectric conversion element according to item 13 . The photoelectric conversion element according to claim 13 or 14 , wherein the layer containing the compound represented by the general formula (1-1) or the general formula (1-3) and the organic-inorganic perovskite compound is a photoelectric conversion layer. The organic-inorganic perovskite type compound contains Pb ^2+, and the compound represented by the general formula (1-1) or the general formula (1-1) after being irradiated with white light of 100 mW / cm 2 for 1000 hours under a condition of a temperature of 298K and a relative humidity of 50%. The photoelectric conversion element according to any one of claims 13 to 15 , wherein the content of the metallic lead in the layer containing the compound represented by the general formula (1-3) and the organic-inorganic perovskite type compound is 10% or less. An organic-inorganic perovskite stabilizer containing a compound represented by the following general formula (1-1) or the following general formula (1-3) .

(In the general formulas (1-1) and (1-3), R ^{1 to} R ⁴ each independently represent a hydrogen atom, a cyano group, a nitro group or a halogen atom. R ¹ and R ² , R ³ and R ^{4 s} may be bonded to each other to form an aromatic hydrocarbon ring.)

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